1. Field of the Invention
The present invention relates to an optometric apparatus for subjectively testing (measuring) visual performance of an examinee's eye such as refractive power.
2. Description of Related Art
Conventionally, there is known an optometric apparatus called a refractor and a phoropter that is arranged to place an optical element in front of an examinee's eye, show to the eye an optotype presented in front of the optical element through it, and based on the visibility of the optotype, subjectively test (measure) visual performance of the eye such as refractive power and binocular visual performance. In addition, there is known an optotype presenting apparatus including a liquid crystal display, by which the optotype is presented. In a binocular vision test using these kinds of optometric apparatus and optotype presenting apparatus, an optotype for a binocular vision test is presented by an apparatus including a polarization optical member that has polarization axes perpendicular to each other and is attached in front of the liquid crystal display, and a polarization optical element compatible with linearly polarized light is placed in front of a right eye and a left eye of an examinee (see U.S. Pat. No. 7,568,801 corresponding to Japanese Patent Application Laid-Open Publication No. 2008-264262). Another example of the optotype presenting apparatus includes an apparatus in which circularly polarized light is used instead of linearly polarized light, and in a binocular vision test using this kind of optotype presenting apparatus, a polarization optical element compatible with circularly polarized light is placed in front of a right eye and a left eye of an examinee.
In order to have the optometric apparatus compatible with both the optotype presenting apparatus in which the linearly polarized light is used and the optotype presenting apparatus in which the circularly polarized light is used, it is necessary for the optometric apparatus to include both of the polarization optical element compatible with the linearly polarized light and the polarization optical element compatible with the circularly polarized light. However, including both the polarization optical elements causes upsizing of the optometric apparatus and an increase in cost.